Re: Low Frequency sound and Blue whales; Noise

From: Peter M Scheifele (acousticp2@juno.com)
Date: Tue Jan 08 2002 - 19:36:11 EST


Hi Sue,

It is my pleasure to help and if you ever would like any further
assistance outside of Whalenet please feel free to contact me at the
University of Connecticut: 860-405-9103 (Voice), 860-445-2969 (FAX)
scheifel@uconn.edu, or at 860-892-9200 (home FAX), or at 860-886-6842
(home phone and wife's home business line). Incidentally, my wife is an
exotic animal trainer by degree and vocation and also teaches with me in
the Animal Science Dept. at UCONN (she deals in mostly terrestrials).

[sue rosenthal] YES, I UNDERSTAND THIS. I ASSUME WHEN YOU SAY
"RELATIVELY HIGH POWER" YOU ARE REFERRING TO THE LOUDNESS OR DB? ALSO,
JUST BECAUSE NAVY'S SOSUS ARRAY PICKS UP THESE SOUNDS, I DON'T SUPPOSE
THAT IS PROOF THAT ANOTHER BLUE WHALE WOULD ALSO PICK UP THIS SOUND? OR
IS IT? [Peter's answer] Yes, I'm referring to either Watts or dB.
Secondly, I should have qualified my answer by saying that we've not only
heard sounds of say, Northern whales but replies from Southern ones in
apparent coincidence with the Northern animal's signal!

[sue rosenthal] INTERESTING! ALTHOUGH TO ME THE DIFFERENCE BETWEEN THE
1,000 MILES THAT A BLUE WHALES CALL CAN TRAVEL AND 1-4 MILE RADIUS ON
LAND IS NOT THAT COMPARABLE. I ASSUME THAT THIS DIFFERENCE HAS MOSTLY TO
DO WITH WHALES VOCALIZING IN SUCH A LOW BAND WIDTH AND ALSO HAS SOMETHING
TO DO WITH LOUDNESS AND THE FACT THAT SOUND TRAVELS THROUGH MEDIUM OF
WATER. [Peter's response] The 1-4 mile path is an analogy as to how
low frequencies are used by animals to cover long distances. Also, given
the difference between the air and water media its no small feat to get a
signal through a forest at that distance similar to the effort required
to get a signal through thousands of miles of water. To get any sound
signal through that much space requires high power (dB) AND low frequency
in concert. Of course the fact that sound travels five times faster in
seawater than in air helps immensely!

Good writing and thank YOU for educating our youngsters! I have a seven
and eight year old boy and girl respectively who love to read because of
folks like you who make it interesting!
Best
Peter

On Tue, 8 Jan 2002 10:01:05 -0800 "sue rosenthal"
<suerosenthal@mminternet.com> writes:
Peter,

Thanks for all 3 interesting answers. I find with WhaleNet that I may
not always learn what I set out to learn, but it's always fascinating.
 I'd actually like to get a little less technical...And I also think I
should reveal why I'm asking these questions. I'm a children's author
and am writing a non-fiction book about cetaceans for Scholastic. I've
been relying mostly on the general (not written for scientific community)
texts and reliable-seeming web sites (American Cetacean Society, etc.)
that are out there. WhaleNet has been incredibly helpful just as a
backup and also because there are interesting questions.

My follow-up question has to do with your answer to question #1. To make
this easier, I've typed follow up questions in CAPS next to your answers.

Thank you for taking the time to help educate!

Sue Rosenthal
-----Original Message-----
From: sue rosenthal [mailto:suerosenthal@mminternet.com]
Sent: Tuesday, January 08, 2002 3:34 AM
To: Suerosenthal
Subject: RE: Low Frequency sound and Blue whales; Noise

-----Original Message-----
From: Peter M Scheifele [mailto:acousticp2@juno.com]
Sent: Sunday, January 06, 2002 4:49 PM
To: suerosenthal@mminternet.com
Cc: ask@whale.wheelock.edu; pita@whale.wheelock.edu
Subject: Low Frequency sound and Blue whales; Noise

Hi Sue,

Great sound questions! Here are a few superficial answers and if you'd
like to get more technical simply come back at me once again!

1. [sue rosenthal] Question: I know blue whales can vocalize at 190
decibels and that their calls can travel underwater for at least a
thousand miles (Maybe farther?) But how does this compare to other
animals? How loud are humans and how loud would a human shout travel
underwater? Elephants?
Peter's Answer: In general, we know that Blue Whales vocalise in a low
frequency band (as low as 2-20 Hz) and that they have been heard via the
Navy's SOSUS array half a globe away from one another. This, owing to
the low frequency (longer wavelength) and relatively high power, makes
sense. [sue rosenthal] YES, I UNDERSTAND THIS. I ASSUME WHEN YOU SAY
"RELATIVELY HIGH POWER" YOU ARE REFERING TO THE LOUDNESS OR DB? ALSO,
JUST BECAUSE NAVY'S SOSUS ARRAY PICKS UP THESE SOUNDS, I DON'T SUPPOSE
THAT IS PROOF THAT ANOTHER BLUE WHALE WOULD ALSO PICK UP THIS SOUND? OR
IS IT? It not only works well in the underwater medium but in air as
well. Katie Payne has sent infrsonic signals that have been clearly
picked up by elephants over a mile away from the source (speakers atop a
van). Elephants may be thought of as essentially analogous to Blue
Whales in this regard. Some ground rodents are the same. I recently did
some research and a paper (in progress) regarding coyotes in which we
found that coyotes (at least in New England) howl at around 500 Hz,
which, incidentally, is not at their best frequency of hearing but well
below it. This is because they need to make the howl heard across their
(approximately) 4 X 4 mile home area through the trees and brush of the
forest. Once again, the low frequency is a triumphant tool. [sue
rosenthal] INTERESTING! ALTHOUGH TO ME THE DIFFERENCE BETWEEN THE 1,000
MILES THAT A BLUE WHALES CALL CAN TRAVEL AND 1-4 MILE RADIUS ON LAND IS
NOT THAT COMPARABLE. I ASSUME THAT THIS DIFFERENCE HAS MOSTLY TO DO WITH
WHALES VOCALIZING IN SUCH A LOW BAND WIDTH AND ALSO HAS SOMETHING TO DO
WITH LOUDNESS AND THE FACT THAT SOUND TRAVELS THROUGH MEDIUM OF WATER.
Please be aware though, that aquatic ears and aerial ones, although
similar in a gross sense, are not the same and we do not know exactly
what whales hear, what constitutues loud ro threshold of pain.

Ahh, humans! Human speech generally occurs at between 2 - 8 kHz and at
varying levels. Before going on I must caution you that we measure sound
intensity in water using different reference levels (for decibel
measurements) than those measured in air. In water the units of measure
are dB re 1 uPa whereas in air the units are dB re 20 uPa (where dB = 10
log times pressure-squared / Pressure reference). The only way to
measure the sound using common type units would be as intensity in
Watts/meter-squared. Speech levels vary from individual to individual and
with respect to the background (intelligibility) but in a relatively
quiet environment at roughly 30 dB re 20 uPa. A human shout will likely
not travel more than a few meters underwater.[sue rosenthal] OKAY. I
MUST ADMIT THAT AS A NON SCIENTIST, THE EXPLANATION OF WHAT DB IS LOST
ME. BUT I THINK I GET THE POINT. YOU CAN'T COMPARE LAND AND WATER-BASED
SOUNDS. HMM. THIS IS DISAPPOINTING. I HAVE SEEN A WEBSITE AND A FEW
REFERENCES IN BOOKS THAT DO, IN FACT, COMPARE WHALES DECIBEL LEVEL TO
LAND-BASED SOUNDS SUCH AS A JET. COMMONLY, THEY SAY THAT A BLUE WHALE'S
CALL IS EVEN LOUDER THAN THE SOUND OF A JET'S ENGINES. THAT IS A
WONDERFUL THING TO PUT IN A BOOK FOR KIDS, SINCE IT SPARKS THEIR
IMAGINATIONS. BUT FROM WHAT YOU'RE TELLING ME, IT'S NOT REALLY AN
ACCURATE THING TO SAY. PLEASE SEE
http://www.enchantedlearning.com/subjects/whales/species/bluewhale/Loudes
t.shtml

2. As for whether or not Blue Whales communicate over such long
distances, I feel the "jury is still out" on that. One has to ask "What
are they communicating about exactly?" To indicate the location of food
sources at such a long distance makes little sense since it would take so
long for the conspecific to reach the site that the food source would
likely be gone. Mating? Perhaps. However, in a short discussion with a
colleague of mine (Dr. Richard Sears) who is the authority on Blue Whales
we have begun to wonder whether or not Blue Whales navigate such long
distances at such depths in the face of some significant changes in
bottom topography that they might actually be using low frequency sound
as a means of "echolocating-for-navigation". If this is so, it would
have profound impacts on our present notions of pod distribution!

3. We have no clear cut evidence of hearing loss in marine mammals
of any type in the world oceans. We DO, however, have a good
understanding of the effects of noise on the mammalian ear (including
whales). In my own research in the St. Lawrence River Estuary in Canada,
I see evidence of potential hearing loss in heavily trafficed areas. The
only way to actually tell is to either have the animal undergo
audiometric testing or to image the ear (CT or MRI). Another colleague,
Dr. Darlene Ketten, has been doing this in studies of the cetacean ear
but little clear evidence has been found (excluding obvious barotauma).
It is a seroius concern though, especially to those of us who study
animal audiology.

We are all trying to get a handle on measuring these effects. Therein
lies the basis for my current research regarding the use of the
articulation index as a measure of hearing impairment (noise
interference) in the wild due to noise.

I hope this helps out!
Best Regards,
Peter

Peter M."Skip" Scheifele LCDR USN (Ret.)
Director of Bioacoustic Research
Animal Bioacoustics/Neuroanatomy
University of Connecticut

On Sun, 6 Jan 2002 10:59:22 -0800 "suer osenthal"
<suerosenthal@mminternet.com> writes:
Hi Peter:

Lots of sound questions:

2. What is the current thinking on whether blue whales communicate over
large distances? I.E. Even if we know their calls can travel long
distances, do we know they use this to communicate?

3. Finally, this is a rather broad question, but do scientists have
evidence of increased incidences of hearing loss in whales in heavily
trafficked oceans? I know that the theory is that increases in noise are
causing problems, but is it feasible to measure this?

Thank you,
Sue

Peter M."Skip" Scheifele LCDR USN (Ret.)
Hunters Road
Norwich, CT 06360

Peter M."Skip" Scheifele LCDR USN (Ret.)
Director of Bioacoustic Research
Animal Bioacou



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